At the Royal Farms on Key Highway, David DeVincentz fills a cup to the brim with ice before pouring in his daily sweet tea. He has money in his pocket to pay for it but knows the clerks will insist he take it free of charge.

"I never, ever expect to be given anything for free," the Baltimore City police officer said. "I always offer to pay. You don't want to insult them by not accepting it. But I always make an offer."

Such freebies are as old as jokes about police and doughnuts — and cups of complimentary coffee. Many restaurants and convenience stores give uniformed police and firefighters discounts to thank them for their service — and even encourage them to frequent the establishments and provide unofficial security. Some have store policies that guarantee the perks.

But police and fire supervisors say public servants must walk a narrow line to ensure that such courtesies don't create an expectation of preferential treatment on either side.

The issue became the subject of controversy this month when three members of the Bel Air Volunteer Fire Company were suspended and a fourth was demoted for suggesting on Facebook that they start a Dumpster fire at a Sonic drive-in restaurant and not respond to emergency calls there after firefighters didn't receive a discount offered to military and law enforcement personnel.

The fire company's chief, Eddie Hopkins, called the behavior "unacceptable" and acknowledged a sense of entitlement among some in his department.

Hopkins plans to meet with his board of directors to discuss beefing up company regulations on what firefighters are allowed to accept as gifts. Company policy requires firefighters to immediately report and turn over money they're given, which is then classified as a donation to the department. For anything else, they're expected to use common sense.

Hopkins, who served 29 years in the Harford County Sheriff's Department, is in his 39th year with the Bel Air fire company. He said he has been offered free coffee and food countless times in his career. He said that while he often turned down the freebies, sometimes courtesy and the situation demanded that he accept it.

"When I have gone in as a police officer, someone will offer you something free and sometimes you make a scene by not accepting it," he said. "Sometimes they insist."

Hopkins said a detailed policy would be difficult to write, as each circumstance is unique. He mentioned local churches that have held picnics benefiting police and fire departments, with free food for the public servants.

"Do we decline that?" he asked. "Do you say no? It's a really tough call to make, because we're part of the community, and it's the community's way of saying thank you. The line is so grey, I don't know where to draw it."

Some say that, in most cases, the line should be drawn against any free gifts. Doug Ward, director of the Johns Hopkins University Division of Public Safety Leadership, said scandals involving escalating improprieties often started as nothing more than a small gift.

Ward pointed to the towing scandal in Baltimore, in which more than a dozen officers have been convicted in a kickback scheme with a towing company. He said any relationship that develops between officers and the public can lead to conflicts of interest.

"When it comes to taking something, sometimes it's a cup of coffee, but three weeks later it's $50, then three weeks after that it's $300," he said. "The best rule of thumb is, just don't take something — even if it's half off or just a free cup of coffee."

But some businesses — and public servants — see the issue differently.

Another regular at the Royal Farms, Baltimore City Police Officer Alan Yuill, stops in once a shift for a free drink. He pointed out that stores benefit from such offers for police.

"It's nice — you come in, you know people here," Yuill said. "And it's nice for them. They have police in and out of here without paying for a security service. I've broken up my share of fights in here."

At 7-Eleven franchises, each store manager or owner is given discretion over whether to allow freebies for fire and police officers. "We would respect whatever policy/protocol the local agency has," spokeswoman Margaret Chabris said in an email.

Kaitlyn Smith, an employee at 7-Eleven on Key Highway for the past year and a half, sat behind the counter around 2:45 p.m. on a recent rainy afternoon. A couple of patrons wandered in, though business was slow enough for Smith to restock shelves and wipe down the Big Gulp machine.